Many pieces of electrical and electronic equipment are made up of "rack mounted" enclosures printed circuit boards that slide into or out of position along fixed immobile racks. There is a strong trend towards operating such equipment continuously during the installation or removal of any circuit boards. During such "hot swapping," it must be possible to access the board of interest very quickly but without compromising safety, grounding, operation and electrical shielding of adjacent boards, and so forth. The increasingly smaller sizes and closer mountings of modular electronic equipment make this a difficult task, in part because both the number and the density of the connecting pins between boards are increasing as the electronics becomes more sophisticated. Thus, accurate alignment of the circuit board into the rack is important, but achieving such alignment can be time-consuming.
One approach to the problems presented by these conditions are board carriers, which are modular frames that fit closely within the rack and can carry a variety of boards of different functions. The carriers are carefully designed to hold the circuit boards in their proper position while the carrier is inserted into the rack along rails. The carriers may be inserted with relatively less accuracy than is required by the circuit board itself, because the design of the rail system provides the needed accurate alignment as the carrier is moved down the rail into the rack.